Background Heart failure is the leading cause for 30-day all-cause readmission. We examined the impact of 30-day all-cause readmission on long-term outcomes and cost in a propensity score-matched study of hospitalized patients with heart failure. Methods Of the 7578 Medicare beneficiaries discharged with a primary diagnosis of heart failure from 106 Alabama hospitals (1998-2001) and alive at 30 days after discharge, 1519 had a 30-day all-cause readmission. Using propensity scores for 30-day all-cause readmission, we assembled a matched cohort of 1516 pairs of patients with and without a 30-day all-cause readmission, balanced on 34 baseline characteristics (mean age 75 years, 56% women, 24% African American). Results During 2-12 months of follow-up after discharge from index hospitalization, all-cause mortality occurred in 41% and 27% of matched patients with and without a 30-day all-cause readmission, respectively (hazard ratio 1.68; 95% confidence interval 1.48-1.90; P <.001). This harmful association of 30-day all-cause readmission with mortality persisted during an average follow-up of 3.1 (maximum, 8.7) years (hazard ratio 1.33; 95% confidence interval 1.22-1.45; P <.001). Patients with a 30-day all-cause readmission had higher cumulative all-cause readmission (mean, 6.9 vs 5.1; P <.001), a longer cumulative length of stay (mean, 51 vs 43 days; P <.001), and a higher cumulative cost (mean, $38,972 vs $34,025; P =.001) during 8.7 years of follow-up. Conclusions Among Medicare beneficiaries hospitalized for heart failure, 30-day all-cause readmission was associated with a higher risk of subsequent all-cause mortality, higher number of cumulative all-cause readmission, longer cumulative length of stay, and higher cumulative cost.